The following hypotheses will be tested: A. Screening for prostate cancer with digital retal exam and psa blood test will reduce the mortality from prostate ca. B. Screening for lung cancer with chest x-ray will reduce mortality from lung cancer, C. Screening for colorectal cancer with sigmoidoscopy will reduce mortality from colorectal cancer, D. Screening for ovarian cancer with palpation, transvaginal ultrasound and ca-125 will reduce mortality from ovarian cancer. All subjects will be aged 55-74.